# Problem: Elemental phosphorus occurs as tetratomic molecules, P4. What mass (g) of chlorine gas is needed to react completely with 455 g of phosphorus to form phosphorus pentachloride?

###### FREE Expert Solution

We will begin solving this problem by analyzing what information we have, to solve this problem:

Firstly, we will need to write a balanced equation for the data provided.

Phosphorous P4 reacts with Chlorine gas to form Phosphorous Pentachloride

Recall that, Chlorine gas - Cl2 exists as a diatomic molecule and the prefix -penta refers to 5 therefore, we can say that the following reaction takes place

P4 (s) + Cl2 (g) → PCl5 (s)

• Write down the number of atoms on the left side and the right side separately.
• There are 4 P and 2 Cl on the left and 1 P and 5 Cl on the right.
• Multiply PCl5  by 4 to have an equal number of P’s (4 and 4, therefore, they are equal).
• Finally, there are 20 Cl on the right side and only 2 on the left. Multiply Clby 10. Now both sides have an equal number of atoms.
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###### Problem Details

Elemental phosphorus occurs as tetratomic molecules, P4. What mass (g) of chlorine gas is needed to react completely with 455 g of phosphorus to form phosphorus pentachloride?